Chlorinated phenols exhibit outstanding germicidal and insecticidal properties and have demonstrated utility as flea repellants, fungicides, wood preservatives, mold inhibitors, etc. In general, biotoxic effectiveness increases with the degree of chlorine substitution. Technical grade chlorinated phenols have been found to decompose readily in the presence of metals, metal chlorides and heat to form large volumes of hydrogen chloride and tar. Product degradation is attributed to the presence of metal ions in storage and process vessels and small amounts of catalyst residue, i.e., aluminum and iron chlorides present in the technical grade chlorinated phenol product. Elevated temperatures are also known to accelerate the decomposition reactions.
In addition to decomposition difficulties, technical grade chlorinated phenols contain some impurities which give rise to objectionable color formation, typically a dark red or dark brown color. Other impurities include a family of high molecular weight compounds polychlorinated dibenzo-p-dioxins, known to have toxic properties. Other polychlorinated polynuclear impurities, the chlorinated phenoxyphenols, are a primary cause of blooming of the impure chlorinated phenol. Thus, high molecular weight impurities in the technical grade chlorinated phenols cause dark coloration, cause blooming and impart toxic properties in the form of dioxins.
Various processes of inhibiting decomposition of the crude chlorinated phenol during distillation are known. The distillation process has also, heretofore, facilitated the removal of dioxins formed. High boiling amines or alkanolamines have been disclosed as useful in stabilizing impure pentachlorophenol against decomposition during distillation (U.S. Pat. No. 3,816,268). Zinc dust or ethylene thiourea have been used to improve color and reduce the chlorodioxin content of impure pentachlorophenol during distillation (U.S. Pat. No. 3,909,365). Free-radical acting substances, e.g., phenols, hydroquinones, organic sulfur derivatives, organic phosphite, amine- and aldehyde-type compounds, have been used to improve color and reduce the chlorodioxin content of impure pentachlorophenol during distillation (U.S. Pat. No. 4,016,047). Polyhydroxy compounds, selected from the group consisting of sugars, polyhydric alcohols, polyglycols, and polyglycol ethers, have been incorporated into impure pentachlorophenol as decomposition inhibitors during distillation (U.S. Pat. No. 4,142,943). Salicylaldehyde and water and Reimer-Tiemann residues from the preparation of salicylaldehyde have also been disclosed as useful to remove impurities during the distillation of pentachlorophenol (U.S. Pat. No. 3,852,160 and 3,852,161).
The variety of materials offered for the purpose of producing chlorinated phenols which are desirable both from the aesthetic viewpoint and the environmental viewpoint is, to some extent, evidence that none is without disadvantage. Some of the materials identified by the prior art are very effective in inhibiting chlorinated phenol decomposition and/or preventing toxic by-product formation; however, neither of these desired results was possible without distillation. The underlying problems that have not been solved, by the prior art, are the formation of dioxins in the crude pentachlorophenol which made the distillation step necessary, and the lack of adequate mold-release properties in either technical grade or distilled product stored in corrosion-resistant vessels.
As an illustration, chlorinated phenols are conventionally prepared by the reaction of molten phenol with chlorine in the presence of a Friedel-Crafts catalyst such as aluminum chloride at temperatures which result in the production of a molten product. When the crude chlorinated phenol exits the reactor vessel in a molten state, further treatment, at temperatures above its freezing temperature, is required to prevent decomposition and toxic by-product formation. The treated chlorinated phenol product then proceeds to a storage vessel having a mold cavity where the mixture cools to a solid product. Heretofore, release of the solid product from the molds in which they are stored has presented severe difficulties. For example, the solid product adheres to the wall of the mold cavity and seriously complicates the subsequent removal and distribution of the chlorinated phenol product. It is desirable to efficiently remove the solid product from the mold cavity thereby providing a clean mold capable of accepting additional molten product. The utilization of an internal release agent in the treated chlorinated phenol product is also highly desirable and would avoid the obvious disadvantages of using an externally applied release agent to the mold cavity.
No prior art has been found which teaches the use of the compounds specified herein to impart mold-release properties to chlorinated phenols in addition to inhibiting dioxin formation and decomposition at high temperatures.